1. Field of the Invention
The present invention relates to a performance apparatus which can simultaneously produce a plurality of musical tones having the same pitch and the same or similar tone colors and, more particularly, to a performance apparatus with which a user can recognize a plurality of musical tones when they are mixed and are produced from one loudspeaker.
2. Description of the Prior Art
As a conventional performance apparatus, an electronic musical instrument comprising a plurality of keyboards, an automatic performance apparatus having a plurality of tone sources, and a combination of the automatic performance apparatus and the electronic musical instrument are known. In these performance apparatuses, an ensemble of keyboards, tone sources, or a manual keyboard and the automatic performance apparatuses is available.
In a performance of a plurality of, e.g., two musical instruments, even if conditions of the same timing, the same tone color, and the same pitch are satisfied, the phase relationships of musical tones formed by the two musical instruments rarely coincide with each other, thus allowing a polyphonic effect.
However, when a single performance apparatus makes performances of a plurality of musical instruments and when the conditions of the same tone color and same pitch are satisfied, musical tones to be formed have the same phase relationship during their tone generation periods. Therefore, a polyphonic effect cannot be provided, and a plurality of musical tones sound like a single musical tone. In particular, in performance apparatuses using rectangular wave tone sources described in Japanese Patent Publication No. Sho 53-3257 and Japanese Patent Laid-Open No. Sho 58-132286, such a tendency is noticeable. In the worst case, two musical tones are in perfectly opposite phases to cancel each other, and no tone can be produced although keys are depressed. For this reason, in such a performance apparatus, an ensemble by a single musical instrument is performed using different tone colors.